Oedema is fluid retention. It used to be called dropsy. Oedema can be most easily seen round the ankles after you've been standing (peripheral oedema). After lying down for a while, your eyes may look puffy and swollen. In severe cases, oedema can also collect in your lungs and make you short of breath.

Mild oedema is common and usually harmless. It may be due to medication, allergies, or more serious underlying disease.

It is important to seek medical attention if you have oedema. Often no particular cause will be found. The most common causes are mentioned below.

What is oedema?

Oedema is a collection of fluid in the spaces between cells of the body. Fluid leaks out of damaged cells. The fluid cannot be simply drained with a needle and may not improve if you take 'water pills' (diuretics).

Types of oedema include:

Idiopathic - no known cause.

Localised - fluid retention in a particular part of the body. It is usually due to injury or an allergic reaction.

Generalised - affects the whole body. It usually causes puffy ankles after standing and puffy eyes after lying down for a while. This may be due to an underlying heart condition.

Cerebral oedema - fluid on the brain, usually due to infection (meningitis) or serious brain disease (stroke or brain tumour).

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Who is affected by oedema?

Women are more prone than men to oedema. Female hormones (progesterone) tend to cause fluid retention so some women notice puffy ankles just before a period. Oedema may occur for the first time at any age if you suffer an allergic reaction or become anaemic. Older people can develop oedema, as they sit for long periods of time. They are also more likely to have underlying heart or kidney conditions that may cause oedema.

What problems can cause oedema?

This list does not include all the possible causes of oedema but lists some of the more common causes.

No known cause (idiopathic)

Idiopathic oedema is the term for fluid retention which it not caused by a known medical condition. It is most common in women and can sometimes worsen as you get older. Although there is no cure for idiopathic oedema, having a healthy diet which is low in salt can make a real difference. Many people with fluid retention are overweight and losing weight can make a big difference to improve the oedema. A gradual weight loss (rather than fasting and bingeing) is recommended. Support stockings and regular exercise are also beneficial. Avoiding long periods of standing can also help.

Heart failure

Pulmonary oedema is often caused by heart failure. Pulmonary oedema means an excess collection of watery fluid in the lungs. The fluid collects in the many air sacs of the lung, making it difficult to breathe. When the heart is not able to pump blood to the body efficiently, the amount of blood staying in the veins that take blood through the lungs to the left side of the heart increases. As the pressure in these blood vessels increases, fluid is pushed into the air spaces (alveoli) in the lungs. This fluid reduces normal oxygen movement through the lungs, which can lead to shortness of breath.

Angio-oedema

Angio-oedema is a condition that can cause swelling of the deeper layers of the skin. These include the dermis and subcutaneous tissues. It also affects the tissues just under the lining of the airways, mouth and gut - that is, the submucosal tissues.

In most cases there is no known cause and it is not clear why it occurs. This is called idiopathic angio-oedema. Although the cause is not clear, in up to half of cases there is a link to an autoimmune disorder. These include chronic urticaria, systemic lupus erythematosus (SLE), or thyroiditis (hypothyroidism). In some cases there are known triggers that can cause the release of histamine, which leads to tissue swelling of angio-oedema. These include allergic reactions and non-allergic reactions to medicines.

Other possible causes of oedema include anaemia, pregnancy and some kidney diseases. A blood clot in a leg (deep vein thrombosis) can make the leg (with the blood clot) swell.

The doctor will want to know when you first noticed the oedema, how long it lasted for and whether you have any other symptoms. It is important to mention if you've started any new medication. You will be given a physical examination of your lungs, heart and blood pressure as well as the part which is puffy. You will probably be asked for a urine sample and to have a blood test. You may need further tests on your heart, and a chest X-ray.

What should you do next?

You should call an ambulance if you experience severe shortness of breath or chest pain. Mild puffiness of your ankles that gets better when you lie down for a few hours, may not need any treatment. In all cases, you should see your GP to find out if there is an underlying cause.

How can I avoid oedema?

You will need to find the underlying cause and try to address it if possible. Idiopathic oedema has no specific cause and is very common. The best approach is to walk regularly, avoid becoming overweight and put feet up on a footstool when resting.

What is the outlook (prognosis)?

This depends on the underlying cause but is generally very good. Most oedema is due to standing too long on a hot day, especially if you are overweight. Any increased risk depends on the underlying cause.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.